Semiconductor devices are formed from a flat, thin wafer of a semiconductor material, such as silicon. The wafer must be polished to achieve a sufficiently flat surface with no or minimal defects. A variety of chemical, electrochemical, and chemical mechanical polishing techniques are employed to polish the wafers.
In chemical mechanical polishing (“CMP”), a polishing pad made of a urethane material is used in conjunction with a slurry to polish the wafers. The slurry comprises abrasive particles, such as aluminum oxide, cerium oxide, or silica particles, dispersed in an aqueous medium. The abrasive particles generally range in size from 100 to 200 nm. Other agents, such as surface acting agents, oxidizing agents, or pH regulators, are typically present in the slurry.
The urethane pad is textured, such as with channels or perforations, to aid in the distribution of the slurry across the pad and wafer and removal of the slurry and grindings therefrom. In one type of polishing pad, hollow, spherical microelements are distributed throughout the urethane material. As the surface of the pad is worn away through use, the microelements provide a continually renewable surface texture.